Presentation of New Adobe Acrobat 6 Compression Methods
for scanned color and bitonal images
featuring an additional comparison to the DjVu file format
Introduction
Acrobat 6 introduces a new compression method for color images: JPEG2000, and a new compression method for bitonal images: JBIG-2. In addition, the PDF Optimizer and the Image Conversion Plugins of Acrobat 6 are able to produce much smaller PDF for color page scans using the new Adaptive Compression engine, as we demonstrate.
The Adaptive Compression engine is optimized for 300 dpi color images. It identifies the black regions of the image (text, lines etc.) and writes them into a JBIG2-compressed bittonal layer. The color regions of the page are then downsampled and stored as JPEG images in the PDF. The degree of JPEG compression is determined by a sliding bar in the Adaptive Compression engine. An image mask, using transparancy, is created to blend the bitonal and color layers of the page together for viewing.
We present below a test case using a color scan, and a test case using a bitonal scan, to illustrate the new compression methods of Acrobat 6.0.
Color Brochure - 300 dpi image
Full Color, uncompressed TIFF file
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827%
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Full Color, LZW (lossless) compressed TIFF file
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100%
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PDF 1.4 using JPEG-Medium Compression
(entire page downsampled to 150 dpi - medium quality)
(created with Adobe Acrobat 6 PDF Optimizer Plug-in)
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28%
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PDF 1.5 using JPEG2000 Compression
(entire page retained at 300 dpi)
(can only be viewed in Adobe Reader 6 or Acrobat 6)
(created with Adobe Acrobat 6 PDF Optimizer Plug-in)
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23%
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PDF 1.5 using Adaptive Compression - high
(used JBIG2 and JPEG compression - can be viewed in
Acrobat 5 Reader or Acrobat 5 also)
(color objects downsampled to 150 dpi - high quality)
(created with Adobe Acrobat 6 PDF Optimizer Plug-in)
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9.3%
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*PDF 1.5 using Adaptive Compression - default
(used JBIG2 and JPEG compression - can be viewed in
Acrobat 5 Reader or Acrobat 5 also)
(color objects downsampled to 150 dpi - medium quality)
(created with Adobe Acrobat 6 PDF Optimizer Plug-in)
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2.4%
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PDF 1.5 using Adaptive Compression - low
(used JBIG2 and JPEG compression - can be viewed in
Acrobat 5 Reader or Acrobat 5 also)
(color objects downsampled to 150 dpi - low quality)
(created with Adobe Acrobat 6 PDF Optimizer Plug-in)
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1.4%
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DjVu-Photo using IW44 compression only
(entire page retained at 300 dpi)
(compare to PDF using JPEG2000 compression)
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29%
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DjVu-Segmented using LT Editor 4.0 clean profile
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1.2%
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DjVu-Segmented using LT Editor 4.0 scanned profile
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1.1%
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** DjVu-Segmented using AT&T default profile
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1.1%
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* best result in PDF
** best result overall
Bitonal Letter - 300 dpi image
Bitonal G4-compressed TIFF file
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100%
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PDF 1.4 using G4-compression
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115%
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PDF 1.5 using JBIG2-compression from Acrobat 6
(can be viewed in Acrobat 5 or 6)
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44%
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*PDF 1.4 using SILX JBIG2-compression for PDF
(can be viewed in Acrobat 5 or 6)
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40%
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** DjVu using JB2 bitonal compression
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24%
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* best result in PDF
** best result overall
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